2.0 Analysis 2.1 Introduction Fire damage to the engines deprived the investigation of some evidence that could have been related to the causes of a power loss in the left engine. Consequently, the analysis will focus on the relationship between the different pieces of evidence found and of their effect on the flight. 2.2 Greyish Smoke The greyish smoke that the witnesses at the runway end saw coming from the left engine may have been caused by oil from a ruptured hose or other major leak spraying on the exhaust stacks. All oil lines in this engine type are internal, except those in the supercharging system. The engine oil pressure pushing against a spring closes the exhaust gas waste gate and impels the supercharger. If one of the supercharger lines had failed, the oil on the engine exhaust system would have produced greyish smoke and the supercharger would have ceased to function because the spring would have closed the waste gate. In addition, it is unlikely that the engine would have been damaged by a lack of lubrication because of the short elapsed time between the appearance of the smoke and the impact. 2.3 Engines On teardown of the left engine, no anomalies were observed that could have prevented the engine from functioning normally. The left supercharger blades were not damaged and the left waste gate was open, suggesting that the supercharger was capable of turning but was not turning at the time of impact. Also, impact marks made by the left propeller on a tree show that the propeller was feathered and the engine was not producing power. These observations were corroborated by the exhaust system analysis. 2.4 Yaw Movement The left turn observed by the witnesses must have been initiated by the yaw caused by the asymmetrical thrust of the engines. The difference between the thrust levels was significant, as the pilot did not appear to have counteracted them quickly. After regaining control of the aircraft, he continued on a descent path. To obtain a rate of climb at the maximum allowable weight, the pilot must retract the landing gear and quickly feather the propeller, among other things. It could not be determined whether the landing gear was retracted after take-off and subsequently lowered. Also, it could not be determined whether the propeller was feathered by pilot input or because of a loss of oil pressure. However, it seems clear that one of these actions or perhaps both were not executed rapidly, as the aircraft continued to descend after the smoke appeared. 3.0 Conclusions 3.1 Findings On teardown of the engines, no anomalies were observed that could have affected the engines prior to the impact. The left engine supercharger was not functioning at the time of impact. The left engine propeller was feathered at the time of initial impact. One of the oil lines in the supercharging system probably ruptured, causing a loss of oil pressure in the engine. Greyish smoke emanating from an engine is normally caused by a major oil leak spraying on the exhaust stacks. The left turn by the aircraft was initiated by the asymmetrical thrust of the engines. The evidence gathered is consistent with a loss of control of the aircraft below VMC. The pilot did not maintain speed above VMC. 3.2 Causes It is probable that a loss of oil pressure in the left engine caused a loss of power just after take- off. The pilot was unable to maintain the minimum control speed (VMC) of the aircraft. The Board has no aviation safety recommendations to issue at this time.4.0 Safety Action The Board has no aviation safety recommendations to issue at this time.